Talk:Compound Poisson distribution
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I assume that E[Y] = λ * E[X]
What is Var[Y] in terms of the distribution of X? Say, if X has a gamma distribution.
[edit] Some properties
E[Y] = E[E[Y | N]] = λE[X]
Var[Y] = Var[E[Y | N]] + E[Var[Y | N]] = λ{E2[X] + Var[X]}
The cumulant generating function
- One could add to the above, that if N has a Poisson distribution with expected value 1, then the moments of X are the cumulants of Y. Michael Hardy 20:39, 23 Apr 2005 (UTC)